The DarkSide-50 experiment, located at Laboratori Nazionali del Gran Sasso
(LNGS), following the results of its predecessor DarkSide-10 [1]},
searches for nuclear recoils (NRs) induced by WIMP scattering with a
liquid argon double-phase time projection chamber (LAr-TPC), surrounded by a
spherical liquid scintillator veto (LSV) located in the center of a cylindrical
water Cherenkov veto. The active veto detectors are used for rejecting the
coincidences in the LAr-TPC induced by cosmic and material radiation (see, for
details, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}).
Two arrays of 19 Photo Multipliers each of 3”, facing from the top and the bottom the liquid argon
active volume (\(\sim 46.4\)  kg), detect the primary scintillation light (whose signal is called S1) and
the gas scintillation from drifted ionization electrons (whose signal is called S2).
LAr intrinsic scintillation characteristics allow us to reject electron recoils (ERs),
essentially beta and gamma events from background, at the level of
\(1.5\times 10^7\)  or even better [3]}. The particle identification is based
on the fraction of S1 detected in the first 90 ns from the pulse start time (\(f_{90}\)  parameter).
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